1. Field of the Invention
This invention relates to a sampling system for collecting a sample in a septum closed container. More particularly, this system provides a reservoir of a predetermined volume which, upon actuation of valves on the inlet and outlet of the reservoir, captures a sample and provides for routing of the captured sample from the reservoir to the septum closed container.
2. Description of the Related Art
In the operation of many chemical and other processes, it is often necessary to periodically sample fluids which are flowing within the process at various points. For a variety of reasons, it is often advantageous to collect the fluid in a septum closed container, e.g., the sample is volatile, the fluid presents a safety hazard if released to the atmosphere, or the sample may be sensitive to absorption of air or atmospheric moisture. Several various designs of septum closed containers and samplers are known. Examples of such septum closed containers and samplers are shown in U.S. Pat. Nos. 4,174,632 and 4,887,472 to Jansen and U.S. Pat. Nos. 4,651,574, 4,791,821, 4,879,915 and 4,986,138 to Spencer.
The systems for collecting a sample with the known septum closed containers and samplers present several disadvantages. First, known samplers and associated systems for collecting a sample may contain a "dead volume" i.e., a configuration which allows fluid from a previous sample to occupy a part of the system or sampler and to contaminate a later sample, leading to inaccurate analysis. Also, known systems for the collection of a sample typically require the operation of several valves. This may lead to error in collecting a representative and consistent sample and is time consuming as it requires special procedures. Here, the technician (person catching sample) must allow fluid to flow through the sample line adjacent the septum closed container. Then, he must open the valve to the septum closed container which again presents several disadvantages. Here, the technician must attempt to fill the septum closed container by opening and closing its inlet valve. This leads to a sample which is not of a consistent volume with previous samples, which may make it difficult for laboratory personnel to effectively manage the samples of varying volume. Also, the technician may have a difficult time in filling the septum closed container without overfilling the container. This is especially a problem with small sample containers. Further, in catching a sample in this manner, the septum closed container is usually subjected to process pressure. If process pressure is unexpectedly high, it may cause the overpressuring and subsequent rupture of the septum closed container. This presents a significant safety hazard in that the person catching the sample may be subjected to harmful vapors or fragmented glass or metal portions of the septum closed container.
U.S. Pat. No. 4,987,785 to Spencer discloses a sampling system which provides for constant volume sampling and includes a section of tubing having a predetermined volume with three-way valves on the ends of the tubing. The system provides for the simultaneous operation of the two three-way valves. While this patent addresses several of the disadvantages presented above, it has several shortcomings which significantly limit its usefulness. First, this patent discloses a chain and sprocket system for simultaneous movement of the two three-way valves. This chain and sprocket system would not function effectively in a chemical plant or refinery environment because the chain and sprocket system would need constant adjustment and maintenance to ensure that the valves are moved simultaneously. Also, this chain and sprocket system could easily "freeze-up" due to the corrosive nature of these plant environments. Thus, this system would not be viewed as reliable by personnel operating a chemical plant or refinery. Also, the configuration of the sample system would allow sample fluid to leak into the pressurized gas line used for transferring the sample fluid from the tubing to the sample container and lead to contamination of the next sample or varying sample volumes. Further, this system does not provide for ease of operation, i.e., it does not provide the person catching the sample with assurance that the system is functioning properly. Still further, this system does not provide adequate safeguards against equipment or system failures which are required in a chemical plant or refinery environment.
There exists a need for a sampling system for collecting a sample in a septum closed container which prevents contamination of a sample by fluid from an earlier sample contained in a dead volume, provides a consistent size sample, allows collection of a sample upon the operation of a single valve, is safe to operate in that the sample container is not subjected to process pressure, and which allows samples to be obtained without overfilling the septum closed container.